merge two sorted lists

Steve Sun · Steve Sun · commit 5fcb20bbdb59 · 2016-10-10T22:24:58.000-07:00
diff --git a/EASY/src/easy/MergeTwoSortedLists.java b/EASY/src/easy/MergeTwoSortedLists.java
@@ -0,0 +1,37 @@
+package easy;
+
+import classes.ListNode;
+
+public class MergeTwoSortedLists {
+
+    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
+        ListNode pre = new ListNode(-1);
+        ListNode dummy = pre;
+        while(l1 != null || l2 != null){
+            if(l1 != null && l2 != null){
+                if(l1.val < l2.val) {
+                    pre.next = l1;
+                    l1 = l1.next;
+                } else {
+                    pre.next = l2;
+                    l2 = l2.next;
+                }
+                pre = pre.next;
+            } else if(l1 != null){
+                while(l1 != null){
+                    pre.next = l1;
+                    l1 = l1.next;
+                    pre = pre.next;
+                }
+            } else if(l2 != null){
+                while(l2 != null){
+                    pre.next = l2;
+                    l2 = l2.next;
+                    pre = pre.next;
+                }
+            }
+        }
+        return dummy.next;
+    }
+
+}
